1. Field of the Invention
This invention relates to an electronic apparatus acting as a host to which a memory unit with a built-in controller IC, such as a memory card, can be connected and a method of controlling the memory unit.
2. Description of the Related Art
With the recent remarkable progress in semiconductor manufacturing technology, memory cards with a built-in controller IC are getting larger in capacity rapidly. This enables electronic devices acting as hosts to which memory cards are connected, such as digital still cameras or digital video cameras, to handle large-volume content, such as moving images or music.
A host which handles large-volume content is required to finish inputting and outputting data to and from a memory card quickly. That is, faster data transfer between the memory card and the host is considered important. For this reason, a method of setting the data transfer speed to a value suitable for each memory card has been proposed (refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 7-320018).
In the method disclosed in Jpn. Pat. Appln. KOKAI Publication No. 7-320018, the data transfer between the memory card and the host is carried out at the access speed specified in the access speed information acquired from the memory card. Therefore, even when any type of memory card is installed, the data transfer best suited to the memory card is performed.
As described above, data is always input to or output from the memory card via the controller IC. Therefore, use of only the optimization of the data transfer speed between the memory card and the host makes it difficult to maximize the performance of the memory card.
For example, the specifications of the memory card, including the block size of the memory built in the memory card and the procedure by which the controller IC accesses the memory, differ from maker to maker or depending on the time when the memory card was developed. When data is input and output by a standardized method without recognizing the difference in the specifications, it is possible that a specific command will be often used for the controller IC even though the controller IC is weak in the access procedure based on the specific command or that data writing unsuitable for the block boundary of the memory will be performed frequently. In such a case, even if the data transfer speed between the memory card and the host is optimized, it is difficult to shorten the time required to input and output the data to and from the memory card. Therefore, there has been a desire for an electronic apparatus capable of maximizing the performance of a memory card, taking the specifications of the card into account, and a method of controlling a memory unit connected to the apparatus.